246 REPORT — 1851 



Nemertinida, the Planarice are provided with ciliated integuments. This 

 general distribution of vibratile cilia over the cutaneous surface, suggests the 

 inference that the milky contents of the digestive tubules, in common with 

 the blood-proper, undergoes a respiratory change. And lastly, a further 

 departure from the type of the Nemertinidce occurs in the Cestoid Entozoa, 

 for in Tania and Sothriocephalus, not only the proboscis and oesophagus 

 disappear, but the mouth also. The digestive system remains, notwithstand- 

 ing, essentially the same. By these observations, the author hopes that an 

 addition of some interest and importance is made to our knowledge of the 

 organization of some of the most curious forms of inferior life. The plan 

 of study which they are well calculated to suggest, may lead, in the hands of 

 others, to much further and more extensive results. They will suffice, he 

 trusts, to divert the attention of physiologists from the blood-proper as the 

 exclusive fluid element of nutrition, to the study of the characters of the 

 great chyl-aque^s system of fluid, of the existence and importance of which, 

 in nearly all invertebrate animals, ample evidence has been adduced in the 

 progress of this Report. They establish the principle formerly enounced, 

 that each constituent element of the living organism, whetliev fluid or solid, 

 in its generic and specific phases is governed by one undeviating law. The 

 fluids obey their law and the solids theirs. Thus the successive members of 

 the zoological series are united at several points, all component systems of 

 the organism displaying a consecutiveness of development, a unity of plan, 

 such that the presence of each in its allotted position is essential to the re- 

 sultant, symmetrical unity of the whole. 



Reproductive System. 



No subject within the domain of comparative anatomy has experienced so 

 much neglect as that which relates to the structure of the organs of repro- 

 duction in the Annelida. The whole process of multiplication in these worms, 

 as explained by M. Duges and Sir E. Home, seems little else than a myth or 

 a fable. A romance or a fairy tale, woven in the picturesque language of a 

 modern fiction-writer, could not prove to the imagination of the practical ob- 

 server more full of mystery and marvel. Since the epoch of these two ana- 

 tomists, no attempt whatever has at any time been made to determine the true 

 characters of the reproductive organs of the Annelid. Milne-Edwards, to 

 whom science owes no ordinary gratitude, has indeed resolved the enigma 

 of the development of one solitary worm, viz. Terehella nehrdosa. It is to 

 be wondered at, however, that, while noting the embryological history of this 

 worm, he did not turn to the parent animal and describe the organization of 

 the parts engaged in the production of the new being. It were to serve no 

 purpose of historical interest to reproduce in this place the descriptions of 

 the earlier anatomists. They contain little of what is true and much of what 

 is false. This statement is not made in the spirit of reproach. Duges' instru- 

 ments of observation, used too on a little restless worm almost itself micro- 

 scopic, could not carry the eye to those details of structure through which alone 

 the real connection and dependence of organs was to be tracked. The ob- 

 servations of Sir E. Home, far less faithful and exact, are still less entitled to 

 repetition in this place. 



The Annelida are commonly reputed to multiply the species, not alone by 

 the production of young, but also hj fission and gemmation. With cha-- 

 racteristic gravity, for example, the learned Hunterian Professor* relates, 

 that " the power of repairing injuries and reproducing mutilated parts is 



* Sections on Invertebrate Animals, vol. i. p. 143. 



